Monday, November 24, 2014

Another chef's knife coming up. Christmas closing in and I need to get these out of the way.

I am starting with a piece of 3/32" 154CM and using the KN9 pattern, but it will be a deeper blade. The original KN9 was intended for 1-1/2" stock and I want to make this blade closer to 1-3/4" deep.

As always I lay the pattern out on the steel. If there are any surface inclusions in the steel I try to keep these at the tang end of the knife or in areas where I know for sure they will be ground away.

After tracing, the bulk of the removal is done with a hacksaw and my
trusty carpenter's vise. A fresh bi-metal 18 TPI (teeth per inch)
hacksaw blade will tear through this steel quickly.

Cut close to the line and leave some room to grind back to the line.

Here I am grinding to shape with an old 60 grit blaze. It's okay to use an old belt for this type of work, but you want to use a fresher belt for the primary grind.

Here the overall knife is taking shape.

For surface grinding I still like my old 4x36 machine. Hold the blank with a magnet and clean the faces. After this I blue the edge so I can scribe the center line.

Her we are back on the 2x72" with a fresh Blaze 60 for making the primary bevel. I like to hold the steel at an angle, say 30° to start and then feather it back with successive passes. As a pattern I work with right hand (strong side) first and do the left hand pass and alternate.

Once the feathering starts I raise the blade off the tool rest and continue making passes.

Here we can see the grind starting to take shape. All in all I may make 100 passes to get the shape looking good and symmetrical. Always stopping to check after each pass or two.

As 60 grit leaves some pretty large scratches, I switch belts here to a 120 grit and work the area again. This will get us ready for some detail sanding by hand.

Friday, November 14, 2014

I like too use a toggle clamp to hold the blade down. I can sand one side of the blade and quickly flip the blade over. It's the cat's meow. I have more ideas on my Shop Jigs & Fixtures page.

Normally I start at the grit I left off with on the belt grinder. If some gouges are deep, maybe roll back a size or hop back on the grinder to clean them up.

Window cleaner is my lubricant of choice for hand sanding. Periodically wipe and give it a quick squirt and start again. Pieces of sand paper will last a few minutes each, so keep plenty handy.

Here's what the blade looks like during the hand sanding process.

Near the end of hand sanding I like to look at the blade and use the reflections to make sure that no rough spots exist. At this stage I am working at 320 grit. Once it's clear we can move on to handle prep.

I really liked how the oval pattern worked on the KN7-2 and wanted to carry some of that skill into this version.

The front bolster will follow the same curves and the scale inset. Note the marking for holes is in a straight line from bolster to bolster.

A punch is used to make sure the drill bit doesn't walk away from the intended spot.

When drilling the holes in the tang, some cutting fluid and a cobalt bit works wonders.

Once drilled, I wrap the blade in stainless steel foil.

Now into the oven for a soak. The target temperature here is 1060°C for 20 minutes. This will vary with steel, but 154CM will be fine at this temp.

Out of the oven and immediately into the plates for quench. You can see some slight oxidization on the blade, but nothing that can't be cleaned up with a light sanding.

Once the blade is cooled to around 50°C (122°F), it goes immediately into the tempering oven at 200°C (400°F) for two hours, cooled and a repeat 2 hours at 200°C. This should produce a hardness around 58 to 59 Rockwell C.

The front bolster for the KN9 will be made of 416 stainless steel. As the bar that I have has been surface ground I used want these flat surfaces to contact the tang.

Essentially the layout is done by placing the knife on the stainless and marking the shapes for the left and right bolster pieces on the bar. When grinding, I like to keep everything as long as possible. This way I have something to hang on to.

After some curves are ground I need to cut the right piece off the bar. Yup, good old hacksaw always works. I continue grinding the left piece as much as I can, then cut it off the bar.

Once both pieces are cut off, align them and clamp them well with the vise-grips. Now you can match the pieces. We are focusing on the whole shape, but special attention to the fronts.

Here's the two pieces rough shaped.

Testing them against the tang for shape.

He I am rounding the fronts of the bolsters with a 120 grit belt. Working on symmetry while maintaining the arc shape.

Looking pretty good. Now switching belts to about a 320 grit.

The bolster pieces are ready to polish.

I have a little bench grinder that I use only for buffing. Some green (stainless) and black (general purpose) polishing compounds make 416 stainless shine like a mirror.

Here's a shot of the front of the bolster pieces. When I finish hand sanding the blade, I'll be able to clamp and drill these for pins.

I scrubbed the blade up a lot with 180 grit then 240 and finally 320 before etching. Then I cleaned the area to be etched with acetone.

With the stencil down and pad whetted with electrolyte solution and etched and marked.

This is the result. Got to love Ernie's stencils!

On the right side I put the steel type. Now a wrap of the blade and we're ready to put the front bolster pieces on.

I line one piece up perfectly and clamp. Making sure the clamp isn't where the drill bit will come through!

A #30 bit makes a perfect hole for 1/8" pins.

After one hole is drilled, put a pin in it. I cut some cheap 1/8" steel rod for temporary pins. Once it's pinned, align and drill the second hole. The reason I did this was the bolster piece is small and difficult to clamp and drill both holes .

Once the second hole is drilled, put a pin in it. Then align the second bolster piece and clamp. Now remove a pin and drill right through. Put the pin back in (all the way through both bolster pieces) and drill the last hole.

Cut some pins of the same material as the bolster pieces, in this case 416 stainless steel. Make them about 1/4 longer than required. This will allow for lots of radial expansion when pressed. Clean the pins with sand paper and clean the holes in the bolster pieces with acetone. Also clean the tang if there's any filings, bluing or felt pen on it.

Place the pins through the pieces and head over to the press.

Here I use some #10 flat washers. These prevent the pins from pressing all the way flush on either side. I give the pins a light press, just enough to make the bolster pieces stay. Then another squeeze of the pieces themselves. These should tight against the tang and no gap visible.

Now press them hard. They will expand and fill the hole with great force.

Now on the grinder with a 60 grit belt and you can see they have disappeared! Perfect.